diff --git a/static/js/recent_senders.js b/static/js/recent_senders.js
index c3e98bd4e3..a85e1de925 100644
--- a/static/js/recent_senders.js
+++ b/static/js/recent_senders.js
@@ -1,16 +1,16 @@
-const Dict = require('./dict').Dict;
 const FoldDict = require('./fold_dict').FoldDict;
+const IntDict = require('./int_dict').IntDict;
 
-const topic_senders = new Dict(); // key is stream-id, value is Dict
-const stream_senders = new Dict(); // key is stream-id, value is Dict
+const topic_senders = new IntDict(); // key is stream-id, value is Dict
+const stream_senders = new IntDict(); // key is stream-id, value is Dict
 
 exports.process_message_for_senders = function (message) {
-    const stream_id = message.stream_id.toString();
+    const stream_id = message.stream_id;
     const topic = util.get_message_topic(message);
 
     // Process most recent sender to topic
     const topic_dict = topic_senders.get(stream_id) || new FoldDict();
-    let sender_message_ids = topic_dict.get(topic) || new Dict();
+    let sender_message_ids = topic_dict.get(topic) || new IntDict();
     let old_message_id = sender_message_ids.get(message.sender_id);
 
     if (old_message_id === undefined || old_message_id < message.id) {
@@ -21,7 +21,7 @@ exports.process_message_for_senders = function (message) {
     topic_senders.set(stream_id, topic_dict);
 
     // Process most recent sender to whole stream
-    sender_message_ids = stream_senders.get(stream_id) || new Dict();
+    sender_message_ids = stream_senders.get(stream_id) || new IntDict();
     old_message_id = sender_message_ids.get(message.sender_id);
 
     if (old_message_id === undefined || old_message_id < message.id) {
@@ -32,8 +32,6 @@ exports.process_message_for_senders = function (message) {
 };
 
 exports.compare_by_recency = function (user_a, user_b, stream_id, topic) {
-    stream_id = stream_id.toString();
-
     let a_message_id;
     let b_message_id;